Production of zinc oxide



Apr. 3, 1923 1,450,704 J. A. slNGMAsTER ET Al.

PRODUCTION OF ZINC OXIDEV Filed Feb. 18. 1920 QW. ESM-44 MYC/Wale ficiently uniform resistance to the air blast to permit the roeess to he continued to snbstantial comp etion.

It an attempt ismade to use an amount of high grade ore comparable to the amount of low grade ore commonly used, together with the necessary eoal for its proper treatnient` it is found that the ganglio constituents in the lower portion of the Charge. after the working' off of the zine oxide and the combustion of the earbonaeeous material therefrom, tend to fuse together and form an imperviouslayer of `*lag or elinker iinmediately ahore the grate. thus interfering with the uniform aetion of the blast. and resulting in uneven workin;i of the eharge. or even in the prevention ofthe further carryingr on of the proeess. As a result` the tendeney to the formation of erarks or of hlowholes or craters at various regions of the Charge ie increased, and it heenies ditlienlt; to maintain a uniform working ott of the eliarge. while a considerable amount of the zine of the upper portions of the eharife remains in the residue. The zine eontained in these residues` eannot ordinarily he recovered eomn'iereially. and is therefore lost.

These objections to the use of Hin-h a thiek working eliarge of high grade ore can he decreased hy reducingr the thieknesa of the working eharge. VWith sneh a thin working eliargp iov-wer. a lower hiaat presisnre musthe en oy: 'while the diflienlty of maintainin; r a uniform distrihntion ofthe hlast is neatly ii'icreaaed, and diflitnlty is still met with from the tenileney towarde` formation of an impervious layer of slag: or elinker inimediately above the grate.

These rliltienltiee in the working ot' high grade zineiferons material ran. h v the proeeee ot' the present invention. he overt-ome or ohviated to ant'h an extent that it heroines poesihle. to employ. in the ll'etherill prot-ess` a workin;r ehare'e eontaining high grade aineiferi-ii|sI material. eoinparahle in thiek4 nea` and amount to the ehargea of low grade zineii'erons material heretofore eonnnonly employed` so that very materially inereaeed yields` or makes; eau he ohlained per Square foot of Pgirate area.

The pioeess otI the pre\ent invention. therefore relates to the treatment of Sui-h high fraile zineiferons material. sneh ae oxidized ores. vroasted or semi-roasted y ullide ores, or ealeined earhonate ores ete. whieh are relatively rilh in zine and free from or lon in lead. so that there will he olitained a zint' oxide whieh is free or rela tively free froxnlead a11d eontaining. for example. not more than three pereent of lead. tiirnled a# lead Sulfate. and prel'erahly lees than one pereent: that is. thiI proee of the inwntion relatee tothe produrtion otI a high ltrade zine oxide of low lead eontentV` as distnigniehrd from products; of relatively high lead eontent. commonly known as leaded 1 oxide.

le have discovered that if a layer ot y eoal is spread uniformly over the la ignition coal, after it has been "pron well developed combustion. and if ing: charge is then Charged into t and spread out upon the layer of the thickness of the working eharife i -zlr i ingr the high grade zineiferona` in: ,i ..i he inereaeed to a thiekness compe: e the thieknesel of the working Y i f' lgrade zineiferous materials herotw t f monly employed, and the reipi' i -f ioioslig of the charge can he therehy maintained throughout the working off operation. and 'a suftieiently inereaeied presesnre of the air hiaat can be need` so that the ehargfe, ean he work ed ott' to `enlistantiai eonipletiom with the if snit that very materially inereased reeoverio, can be obtained from the heavier hurdeiie` thus employed. that is, very materially n ereased recoveries of high grade zine oxide can he time obtained from fnrnaeee` of the Same I:irate area heretofore employed in the produetion of very n'iateiially lese amounts? of zine oxide. High grade zinrileroneI ma` terial of the eharaeter ahove referred to; sueh as oxidized ores, roasted sulfide oree or eoneentratee or ealeined earhonate ores or eoneentrate. ete. .eineh aS have heretofore heen eonnnonly need in the mannfaetnre of Shelter. eau. aeeording to the pressent invention. he ad fantageonsly employed in the mannfartnre of Zine oxide. Ures or eoneentrates.. for example. flotation eoneentratea. ran thus he employed` which. after roasting. eontain from o to T0 per rent or more of zine, that is. of very materially higher zine content than the low grade ores eontainiifi;r for example` St per eent or leas of zine. Sneh as have commonly heretofore heen employed in the praetiee ot' the 'etherill process,

'e have also diseovered that the treatnient of gnrh h igh grade ores ran he fnrther improved h v admixing slate eoal with the wol-hintr eharge. so that there is het?. a layer of the slate eoal hetween the ngi eoal or ignition eoal and the working eli-.inge` and further amounts of slate eoal adinixed with the working eharge itself. "l'he layer ot' slate eoal thus, employed eon trihutes to the prof-esa hv -the eomhuetion ot' it eontained eoal and hy proridintlr a poroto4 distrilulting layer hetn'een the i1- nition i-oal, and the working charge. while the slate eoal ailmixed with the working hai-ge eontrihntes in a Similar manner to the maintenaiu'e ofthe charge in a sntlirient mit .Ul porosity for the satistaetoijv earrying out of the 'etherill proeess. ll'wn though the Penligne eonetitntents oi' the high grade ore may tend to fuse and torni :i slag this slag' will he prevented from matting gether and forming a layer whieh will ltltl the grate. The slate 'coal itself `is substaw tially uonslag'ging and retains its form until the eari'mnaeeruisportion thereof has been removed;V while whatever sintering takes place thereafter does not interfere with the proper working of thc charge. Accordingly. a .sullieient air blast can be i'oreed through the eliarge and with sullieient uniformity` so that. as above noted, the working charge can be Worked olf to substantial completion, with resulting high recovery and increased production from the high grade ore employed.

The nature and :ulvantagesr of thefinvention. and the invention itsell. will he t irther illustrated from the following speci 1e eX- ample. Showing comparative results ob tained by the practice of the invention. and by the practice otl the lVetherill process without a layer of slate eoal between thc firing coal and the charge or slate' coal mixed with the Charge. representative analysis of the ore employed is as tollows:

Zn() e9. nuff,` Pf() 0.15); S 5. eoz, SiOL. 2. 5% Fe() 12.0% Ca() 2. 5@

Two furnaee blocks were worked with the ore. The ehar` for each charge door. that is, one-third o the charge for eaeh furnace. in each ease, was as follows:

Roasted sullid ore tvfltllbs. (lll'llhs. Coal in charge tlzlllbs. 0201bs. Slate coal in charge 2501bs. Firing coal .l'llbs. 250lbs. Slate on firing coal 2001bs.

the air blast gradually until the full air blast had been attained at about one hour before drawing the lire. It was thus found Vpossibleto use an average of about 44) per eent more air with the furnaces in which the slate coal was employed (in the manner above deserila-d) as compared with the furnaees where the slate eoal was not employed.

The amount olt elinlter obtained and the zinc oxide and carbon content thereot'` are,

given below. The amounts given are from a eharge three times that above` given. that is. from one furnace. while the charge above given is for eaeh charge door or for one third ol the l'urnace.

Percent of Zno() ehargelhl It will be noted that a mueh greater loss of zine oxide took place where the slate coal was not employed (in the manner above described) than when it was so employed; while the Weight of the clinker obtained when the slate coal was employed is very materially increased in amount, owing to the slate content of the slate coal so used.

The bag-room recoveries obtained in each ease showed a recovery'of about T1 per cent. over a period of several days, as compared with an average recovery ot' more than 84 percent from the furnaces Where the slate coal was employed. 1

The low recovery ofl "/f. is too low for commercial operations. In order to increase the recovery (when slate coal is not employed) to above 80% it is necessary to reduee the burden of the high grade ore to such an extent that the yields are not materially greater than with low grade ores, e. around 950() lbs. zine oxide per 24 hours from one block (of four furnaces). There slate coal is employed (in the manner above described) with high grade ore. it is possible to increase the yield to around 16.500 lbs. per 24 hours or even higher` from the same grate area. while still obtaining high recoveries, such as above referred to.

Instead of employing slate coal in the manner above described, other materials may be employed which are substantially non-slagging and which serve to provide a porous distributing layer between the igni tion coal and the working charge. Slate alone or bone coal may thus be employed. as Well as other materials of a suitable character. The material should be of a suitable size, preferably between about one half inch and one inch. The material which We eon- Sider most advantznfreous.` however. is slate coal. preferabl the portion rejected in the preparation o anthracite coal by jig'ging, inasmuch as it contributes combustible material to the process, as well as a substantially non-slagging material. and inasmuch as the presence of the coal intimately admixed with the slate improves the action of the slate for the purposes of the invention. f ccordingly we recommend slate eoal as the material to be used when it is available inasmuch as it is a Waste product commonly found in large amounts wherever coal is` mined, it is readily obtainable in large amount and at moderate expense. lVhere bituminous shalcs of suitable character are available, these can be used in a similar manner.

\'l`he layer of slate coal (or other material) can be employed alone, Without admixture of further amounts of slate coal with the working charge. and we consider this to be a characteristic feature of the invention, irrespective of whether further amounts of the slate coal are employed in the working charge. However, it will usually be more advantageous to supply further amounts of the slate coal to the working charge, so that there will be obtained both the advantages of the layer of slate coal between the layer of ignition coal and the working charge, and the advantages of the slate coal admixed with the working charge itself.

The single figure of the accompanying drawing diagrammatically represents the invention as carried out in a furnace of the VVetherill type. As indicated in the drawing. the furnace has a flat horizontal grate 1 composed of heavy cast iron sections with slot perforations to permit of the passage 0l air through them. Beneath the grate are ash pits 2 where the material falling through the grate accumulates and is removed from time to time through suitable ash-pit doors 3. The furnace is'cornmonly constructed of fire brick within and red brick without and provided with the usual stays and supports (not shown). The capacity of the furnace is determined by the arca of the grate. This grate may, for example. have a length of about 1992 feet and a width of about 6 feet. the top ot the arch 4 being about 3 feet above the top of the grate. The furnace has a plurality of charge doors .5 through which the various constituents of the charge are spread upon the grate after being dumped down through suitable holes 6 in the top of the furnace provided for this purpose. The fume-laden gases are conducted from the furnace through upright pipes 7 which communicate in the well un derstood man ner with a suitable bag-house for collecting zincoxide. As indicated by the legends on the accompanying drawing, a layer of non-slagging material is charged into the furnace between the layer of ignition fuel and the working charge, the latter containingr high grade zinciferous material with or without admixturc of further amounts of non-slagigging,r material.

lVhat we claim is:

l. ln the production of zinc oxide by the Yetherill process from a working charge contaiuin,|, r high grade zinciterous material relatively low in ganguc constituents. the step of supplying a porous distributingr layer ot substantially nonvslaggings,r material between the ignition fuel and. the Working charge; substantially as described.

2. In the production of zinc oxide by the 'et-hcrill process from a Working charge containing high grade zinciferous material relatively low in gangue constituents, the step of supplying a porous distributing layer of substantially non-slagging material between the ignition fuel and the working charge, together with the ste of adding,r Yfurther amounts of such material in admixturc with the Working charge; substantially as'f'described. Y

3. ln the production of zinc oxide by the Wetherill process from a Working charge containing high grade roasted. or semi-roastcd sulfide ores or concentrates lor calcined carbonate ores or concentrates, the step ot supplyingr a porous distributing layer of substantially non-slagging material between the ignition fuel and the working charge; substantially as described.

4. In the production of zinc oxide by the lVctherill process `from a Workingr charge containing high grade roasted or semi-roasted sulfide ores or concentrates or calcined carbonate ores or concentrates, the step of supplying a porous distributing layer ot' substantially nonsslagging material between the ignition fuel and the Working charm. to gether with the step of adding iliirthor amounts of such material in admixturc with tbe` working charge; substantially as described.

5. In the production of zinc oxide by the lethcrill process from a Working:` charge containing;r high grade zinciferous material relatively low in ganglio constituents, the `step ot' supplying a layer of slate coal lieiween thc ignition fuel and the working;` cha rgc; substantially as described.

(i. ln the production of zinc oxide by the lVetherill process from a working charge containingr high z,c frade zinciferous material relatively low in gangue constituents, the step of supplying a layer of slate coal between the ignition fuel and the working charge, together with the step of supi'ilyiug further amounts of slate coal in admixture with the working charge; substantially as described.

T. ln the production of Zinc oxide by the ilctbcrill process from aum-king! charge con taining;` high grade roasted or semiroasted sulfide ores or concentrates or calcined cai.'- bonate ores or concentrates. the step of supplying a layer of slate coal between the ignition fuel and the Working charge; subst-antially as described.

H. In the production of zinc oxide by the -ll'etherill process vtrom a` Working charge containing high grade roasted or semi-roastcei sulfide ores or concentrates or calcined E). The method of smcltingf volatili/,utile nwtnll of the nature of lend n1l '/.inc p11!" i0 tivulniiy applicable tu prut-tim? with a gromt furnace which comprises providing :1Y bed Certificate of Correction.

hat in Lvttm's l'nhnt, No. [550304, granted April 3, 1923, pmi the appiivntion nf James Singnmsn-v um! lfvnnk Breyer. 01' Palmei'wn- Pennsylvania, for an imprm'cnwnt '1n irmuvt'm uf Zm- Oxidv." urrnrs uimear in the printed spcvifivatimi vvquiring mn'rurlnn fuiinws: Page l, line H0, for the word "takes rend mlm,- pzigv 2. linv '.IX. fur the misspviiml wol-l "beanies" rend fmcomf's, and liuc T3. :ifll-r tiw win-.l mui sti-ikv ont thv pm'imi und insiri n vm'nnm? Dlllv 3, Iinn 2G. fur li'U" wml MJ. nini iinc T5. fm' "'/mn()" ril-.ul Zul): pa e 5, lint'v 10. riuim l'ur thv wurd gwn! rvzui 'ruw/1f.' nml tlan lim. said ltte-rs I aient. shunld be wml with thi-: 1- i-nrrvrtinus tiwri'in ihm the Mime may confumi tu the revnrrl of thv. vnsv in liw lnwnl (Hiicv.

Signed :md seaied this 5th luy n1' .hum IJ.. w23.

1t is hereby certiierl t [smh] KARL FEN NINH,

A ating I'o-mmz'ssimle-r of Pata-nts. 

